The invention relates to electric fuses and to preassemblies and subassemblies used in the construction of electric fuses.
Electric fuses are used to conduct current under normal conditions and to break a circuit under overload conditions, by the melting of fusible elements of the fuses. In some fuse applications, e.g., where the fusible elements are not visible, it is desirable to have a blown-fuse indicator that provides a visual indication that a fuse has blown.
Fister U.S. Pat. No. 3,281,555 discloses a fuse that includes a spring-loaded indicator pin that is restrained from movement and maintained in a cocked position by a restraining wire that is electrically connected in parallel with fusible elements between two conductor blades that extend from a fuse housing. The space in the housing between the fusible elements and the blades is filled with an arc quenching material (e.g., sand) that facilitates the extinguishing of arcs during fusing of the elements. The indicator pin is mounted within a metal indicator housing that is supported on an upper insulator plate between the conductor blades, and a lower insulator plate is used to anchor a tensioned end of the restraining wire.
Cuzzone U.S. Pat. No. 4,060,786 discloses an electric fuse with a spring-loaded, blown-fuse indicator mechanism having a restraining wire that is restrained and maintained under tension by friction between a plug and a mating bushing that seal off a hole of a cup formed in the end cap of the fuse.
Swaine U.S. Pat. No. 3,764,949 discloses an electric fuse in which fusible elements are provided as part of a multiple-element conductor array that is soldered within grooves of conductor strips after assembly of the strips into a fuse housing. A spring-loaded indicator mechanism is carried by a cap and restrained from movement by tensioned restraining wires that pass through the cavity in which the fusible elements are located.
Jacobs, Jr. U.S. Pat. No. 4,125,819 discloses a cylindrical fuse in which grooves in circular terminal plugs receive the ends of individual fusible elements that are joined together by insulator plates.